If they have an idea who this perp is, then yes, the DNA on the backpack and the water bottle will finish him, most likely.
If it has to go to IGG, that's a longer bet and depends a lot on his background. If he knows that some of his relatives are the type to submit to open databases, he would be better off skipping the country ASAP. He needs to avoid that cheek swab.
I get the feeling that this is a man who values outsmarting LE and is treating each day at large as a bonus to having completed his main goal (revenge). That makes him a bit of Tom Ripley character.
I showed his picture to some students and they said there was nothing memorable about him and they doubted they could remember that "average face." One asked if it was Bryan Kohberger and said he resembles him. While some people are excellent at storing databases of faces, most people aren't.
He can rely on a hoodie and a scarf to mask a lot of what is distinctive about him. He's probably not going to be smiling in public so frequently.
I too believe he went "back home" (where ever that is) and will wait this out. I predict he's something of a loner, but does have family somewhere (but they are unlikely to turn him in). He will likely change his hair and grow facial hair. As time passes, the average Joe Public will not remember or recognize him - but LE will be looking for him.
If he was able to leave the country before the entire story broke, that would make this a very well-planned assassination indeed. I am assuming that JFK no longer has luggage lockers, but I too have pondered whether he had another backpack stashed out in the park, not far from where he dropped the first one. I also ponder if he masked his fingerprints (easy enough to do).
IMO